1. Field of the Invention
This invention relates to multiple component meltblown fibers, multiple component meltblown fiber webs, and composite nonwoven fabrics that include multiple component meltblown fibers. The meltblown webs of the invention can be incorporated in composite fabrics suited for use in apparel, wipes, hygiene products, and medical wraps.
2. Description of Related Art
In a meltblowing process, a nonwoven web is formed by extruding molten polymer through a die and then attenuating the resulting fibers with a hot, high-velocity gas stream. In the production of a web comprised of meltblown fibers, it is sometimes desirable to form the fibers from more than one polymeric material where each material can have different physical properties and contribute different characteristics to the meltblown web. A conventional way to form such fibers is through a spinning process where the polymeric materials are combined in a molten state within the die cavity and are extruded together as a layered multicomponent polymer melt through a single spin orifice, as described in U.S. Pat. No. 6,057,256, which discloses the meltblowing of side-by-side bicomponent fibers onto a collector to form a coherent entangled web.
However, this method has significant limitations due to the compatibility constraints placed on the selection of the polymeric materials such that they will spin well together.
Meltblown fibers have been incorporated into a variety of nonwoven fabrics including composite laminates such as spunbond-meltblown-spunbond (“SMS”) composite sheets. In SMS composites, the exterior layers are spunbond fiber layers that contribute strength to the overall composite, while the core layer is a meltblown fiber layer that provides barrier properties.
There is a need to provide a new method for forming meltblown fibers, and corresponding meltblown webs, that is more suitable for producing multiple component meltblown fibers, and in which the processing conditions for each polymeric component can be optimized individually.